#define _CRT_SECURE_NO_WARNINGS 1

class Solution
{
public:
    string removeDuplicates(string s)
    {
        string ret;

        for (auto ch : s)
        {
            if (ret.size() && ret.back() == ch) ret.pop_back();
            else {
                ret.push_back(ch);
            }
        }

        return ret;
    }
};